Fig. 1

The lichen Cladonia grayi. The most conspicuous parts of the Cladonia thallus are the goblet-shaped podetia that support the sexual and vegetative reproductive structures: the goblets’ upper margins are covered with brown fungal apothecia, sites of meiotic spore production and ejection into the air; the podetial surfaces are covered with green vegetative propagules called soredia, which are tiny alga-fungus packets detached by rain and wind and able to grow and differentiate into full thalli. Soredia are continuously produced and extruded onto the podetial surface from the underlying fungal tissue, which has algae embedded in it. The ground is covered with the less conspicuous, leaf-shaped parts of Cladonia called squamules (yellow arrowhead), which are tiny but fully differentiated lichen thalli with typical medullar, algal, and cortical layers. The grass-like bodies are bryophyte initials. The focus-stacked photograph was taken in D.A.’s lab by Thomas Barlow, who holds the copyright and consents to its use in this study